The present invention relates to a device for positioning a chopper plate on roll with magnetic fixing.
The chopping of cardboard blanks principally employs two essential techniques, namely the so-called SK (xe2x80x9cSingle Knifexe2x80x9d) process in which the cardboard blank is admitted between two associated rolls, namely a chopper roll and an impression roll, and the so-called TK (xe2x80x9cTwin Knifexe2x80x9d) process in which the cardboard blank is admitted between two chopper rolls, of which the impressions are strictly located one with respect to the other.
These different techniques are used conjointly either with one-piece solid rolls, or with rolls on which segments are added. It is known that these two types of rolls are of relatively high cost and this is why it has been proposed to employ plates which are both covered by the impressions necessary for the formation of the chopping or the marking of fold, and which are fixed on a support roll by various fixation means.
A first means consists, after location and positioning, in welding the plate on the support roll by its two ends. However, such a technique presents the drawback of requiring considerable mechanical means for ensuring the tension and a perfect application of the plate on the support roll.
A second, so-called xe2x80x9cfixation of ARK typexe2x80x9d means, consists in disposing, on one of the faces of the plate, at each of the longitudinal ends thereof, a parallelepipedic maintaining element, each maintaining element being fitted in a longitudinal groove provided on the surface of the roll. In such a device, the tension is ensured by a system of wedges which tends to bring the two parallelepipedic elements nearer each other. A drawback of this type of technique is that it requires, in order to be efficient, a tension which is constant on the plate and which is distributed equally over the periphery of the roll.
A third means for fixing the plate on the support roll consists in employing magnetic means which are essentially constituted by magnetized bars which are fitted in longitudinal grooves provided on the periphery of the support roll.
The plate maintaining devices of this latter type are inexpensive and easy to use. However, one drawback of this technique is that, once the plate is positioned on the roll, it is no longer possible to proceed with a correction of its positioning, however small. Now a precise positioning, particularly when the chopping is effected by the TK technique, is essential for the correct functioning of the system. This is why such a type of fixation is not used when an extremely precise positioning of the plate on the roll proves necessary.
Concerning the positioning of the chopping impressions in the sense of the longitudinal axis of the roll, it is known that the chopping machines are provided with means ensuring such a displacement of the support rolls so as to compensate any offset in the longitudinal direction. Similarly, the plate support rolls are provided with means ensuring an angular compensation of one roll with respect to the other, particularly by acting on gears ensuring drive thereof.
The present invention has for its object to propose a means ensuring both the correction of the orientation of a chopping plate in the transverse direction of the roll and the correction of the relative angular positioning of two associated rolls.
The present invention thus has for its object a device for positioning a plate on a roll, in particular a chopper or folding roll, characterized in that the roll is provided on the one hand with magnetic fixing means maintaining the plate on the surface thereof, and on the other hand with two centering elements of which at least one is mobile and longitudinally spaced apart from the first, so as to cooperate with complementary means of the plate, the mobile centering element being linked to control means for displacing it at least along the transverse axis of the roll.
In a first form of embodiment of the invention, the positioning device will comprise a centering element fixed with respect to the roll, so as to ensure an orientation of the major axis of the plate with respect to the transverse axis of the roll.
The present invention also makes it possible, when the two centering elements are mobile elements whose displacement is effected along the transverse axis of the roll, to displace the plate parallel to itself, which amounts to rotating it about the roll, thus ensuring an angular offset of this plate with respect to the plate disposed on the roll associated therewith.
The centering elements will preferably be constituted by studs and the complementary elements will be constituted by orifices provided in the plate. The studs will preferably be constituted by cylindrical elements of circular cross-section. In the case of one of the studs being fixed with respect to the roll, the orifice corresponding to the mobile stud may present a shape elongated in the longitudinal direction of the axis of the roll, its other dimension corresponding strictly to the outer diameter of the stud.
The control means may advantageously be constituted by a lever mounted to pivot about a pin fast with the roll of which one end will comprise a marking element fast with the other side of the plate and which will be adapted to effect an angular displacement under the action of control means disposed at the other end of the lever.
The control means may be constituted by a screw provided with a control knob comprising a vernier for adjustment.
The control means may also be constituted by a system comprising a sloping shim mounted to move substantially in a plane tangential to the roll and inclined with respect to the longitudinal axis thereof, on which shim the mobile centering stud is arranged.